1. Field of the Invention
The present invention is related to a television demodulation, and particularly related to a video standard detector which determines a video standard a baseband signal belongs to and a video standard detection method.
2. Description of Related Art
Generally, in applications of analog TV, a tuner is usually used to down-convert TV signals from a radio frequency (RF) band to an intermediate frequency (IF) band, and the IF demodulator is used to demodulate an IF signal to a Composite Video Broadcast Signal (CVBS) and an audio signal.
There various types of different video standards for the CVBS according in different regions. Currently, the CVBS include three standards such as National Television Systems Committee (NTSC), Phase Alternating Line (PAL), and Sequentiel Couleur á Mémoire (SECAM). The aforementioned three standards all adopt Amplitude Modulation (AM) methods, wherein the AM method may be divided to two types such as a positive modulation mode and a negative modulation mode.
The NTSC video standard belongs to the negative modulation mode, and a field period thereof is approximately 16.67 microseconds. The PAL video standard belongs to the negative modulation mode, and a field period thereof is approximately 20 microseconds. The SECAM-L video standard is one branch of the SECAM video standard and belongs to the positive modulation mode, and a field period thereof is approximately 20 microseconds.
Therefore, at a stage of demodulating the IF signal, it is required to first determine the CVBS specification the IF signal belongs to such that a correction CVBS is demodulated.